Plastic bag flaring apparatus

ABSTRACT

In order to cause the opposing panel ends of a plastic bag to curl outwardly, the bags are captured between moving belts with a portion of their upper surfaces extending above the belts. The outer surfaces of the bag panels are heated, and the panel edges are forced to flare open by passing through a stiff wire. The interior surfaces of the open panel lips are then rapidly cooled to introduce a permanent tendency for the bag panels at the bag opening to curl away from one another.

PATENTEDnm 24 I972 13. 700.367

SHEET 1 [IF 2 F|G. FIG.2

COOLING AIR HEATED- AIR minnow 24 m2 3.700. 367

SHEET 2 UF 2 HOT COLD AIR AIR SUPPLY SUPPLY RELATED U.S. APPLICATION This is a divisional of application Ser. No. 629,328 filed Apr. 7, 1967, now US. Pat. No. 3,629,389.

This invention relates to plastic bags, and more particularly relates to a novel process and apparatus for imparting an outwardly curling or flaring tendency to the upper opposing panels of a plastic bag.

It is well known that it is sometimes difficult to separate the opposing panels of aplastic bag at the open end thereof because of a tendency of the panels to cling to oneanother. This is especially inconvenient in bags for packaging fertilizer, or the like, where an operator must take a bag from a stack, open the bag, and place it in a filling spout which automatically, and at pretimed intervals, ejects a particular weight, such as fifty pounds of the material to be packed. If the operator cannot open the bag quickly enough to place it on the spout, the load will be deposited on the floor, and in some cases, on the operator.

In accordance with the present invention, the bags are caused to have their opposing panels, at the top opening of the bag, flare or curl outwardly so the bag can be easily opened. This outward curl is formed by first heating the upper outer surfaces of the panels, and then opening the panels and rapidly cooling the interior surfaces of the panels. This treatment sets up differential stresses in the plastic which imparts a permanent outwardly curling tendency in the bag around the exterior and originally heated surface.

Accordingly, a primary object of this invention is to simplify the opening of plastic bags.

Another object of this invention is to provide an inexpensive process and apparatus for imparting an outward curl in the top panel sections of a plastic bag.

These and other objects of this invention will become apparent from the following description when taken in connection with the drawings, in which:

FIG. 1 shows a plastic bag in perspective, exposed to heated air at the upper portions of its opposite panels.

FIG. 2 shows the bag of FIG. 1 in perspective, after the top portions of the panels have been flared open and cooling air is applied to the interior surfaces of the panels.

FIG. 3 shows a cross-sectional view, in perspective, of the permanently set outward flare of the plastic bag panels after the treatment of FIGS. 1 and 2.

FIG. 4 shows, in perspective, a portion of the apparatus of the invention including the conveyor belts and opening wires.

FIG. 5 shows a side plan view of FIG. 4, and additionally shows one of the side heaters and the cool air supply.

FIG. 6 is a top view of FIG. 5 and shows the location of the two heaters, the cool air supply, and idler rollers for maintaining belt tension on the bags.

Referring first to FIG. 1, there is illustrated a plastic bag 10 having a front panel 11, a rear panel 12, and an open end 13. The bag may be formed of any desired thermoplastic material, such as polyethylene, having a density of from 0.915 to 1.5, typically 0.925, and a thickness of from 2 to 20 mils, typically 5 mils. In accordance with the invention, heated air; shown by arrows 14 and 15 is directed at the upper portions of panels 11 and 12, heating the surface thereof to about 220F. Thereafter, the bag lips are opened, as shown in FIG. 2, and the inner surfaces of the top portions of panels 11 and 12 are quickly cooled by a blast of cool air, shown byarrows 16, to from 34F. to F. Any type of cooling medium could be used in place of the air 16, such as a water spray or mist. This cooling will cause a permanent outward curl in the upper panel portions of panels 11 and 12, as shown in FIG. 3 by curled sections 17 and 18, which is retained until'the plastic is reheated to about 220F. which relieves the internal strains causing the curling action.

FIGS. 4 to 6 illustrate a novel apparatus for economically carrying out the process of FIGS. 1, 2, and 3. Referring to FIGS. 4 to 6, the apparatus comprises two counter-rotating belts 30 and 311 which are carried on spaced rollers 32-33 and 34-35. Suitable drive rollers 36 and 37 are connected to rollers 33 and 35, respectively, (FIG. 6) to cause the belts to rotate in the direction shown by the arrows at about 60 feet per minute. If necessary, idler rollers 38-39, 40-41 and 42-43 can press the belts together, as shown. The conveyor may have any desired length such as 6 feet, and bags, such as the bags of FIGS. ll, 2, and 3 are loaded between the belts 30 and 31 at the left-hand end of the belts. About 2 inches of the bag top are exposed above the top of belts 30 and 31.

FIGS. 4 to 6 show four bags 50, 51, 52, and 53 loaded between belts 30 and 31, where each of bags 50 to 53 may be identical to the bag of FIGS. 1 to 3.

Two sources of hot air 54 and 55 are located above belts 30 and 31 and direct heated air toward the upper exterior exposed surfaces of the bags as they progress past the heaters. The bags then engage a series of fixed and rigid wire hoops, or the like, such as wire hoops 56 to 59 whichhave transverse lower surfaces which engage the bags about 1 inch below their tops. The wires have the effect of opening the bag tops, and holding open the bag tops as they traverse below the wire hoops.

The bags which have been opened in this manner then pass below a cool air blast from duct 60, shown in FIGS. 5 and 6. The cool air supply may be replaced by a water or mist spray. The effect of this cooling is to impart a permanent outward flare, or curl, in the upper end of the bag panels, as shown in FIG. 3.

Although this invention has been described with respect to its preferred embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and it is preferred, therefore, that the scope of the invention be limited not by the specific disclosure herein, but only by the appended claims.

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. Apparatus for forming an outward curl in the upper surfaces of the opposing panels of a plastic bag comprising first and second conveyor belt means positioned adjacent one another and defining clamping means for clamping a bag therebetween and conveying said bag along said conveyor; motor means connected to said first and second conveyor belt means for driving said first and second conveyor belts; heater means positioned directly above said first and second conveyor belts for directing a heated fluid immediately above conveyor belts, and distributed along the length of said first and second conveyor belts; and cooling means positioned above said first and second conveyor belts fordirecting a stream of cooling fluid toward said first and second conveyor belts. 

1. Apparatus for forming an outward curl in the upper surfaces of the opposing panels of a plastic bag comprising first and second conveyor belt means positioned adjacent one another and defining clamping means for clamping a bag therebetween and conveying said bag along said conveyor; motor means connected to said first and second conveyor belt means for driving said first and second conveyor belts; heater means positioned directly above said first and second conveyor belts for directing a heated fluid immediately above and generally transverse to said first and second conveyor belts; said heater means positioned adjacenT one end and the beginning of the run of said first and second conveyor; a plurality of fixed transverse members positioned directly above said first and second conveyor belts and transverse to said first and second conveyor belts, and distributed along the length of said first and second conveyor belts; and cooling means positioned above said first and second conveyor belts for directing a stream of cooling fluid toward said first and second conveyor belts. 